The voltage-current characteristics of the voltage non-linearity type resistor are generally given in terms of the following expression: EQU I=(V/C).sup..alpha.
wherein
V is a voltage applied on a resistor, PA0 I is a current flowing through the resistor, PA0 C is a constant corresponding to a voltage generated when a given current is flowing, and PA0 .alpha. is an index of a non-linearity coefficient.
The larger the index .alpha., the better the non-linearity will be.
The voltage non-linearity type resistors used heretofore are based on SiO and ZnO. The SiO base resistors are prepared by sintering of SiO particles having a grain size of about 100 microns, and their voltage non-linearity characteristics are adjustable by varying the number of grain boundaries in the flowing direction of current. However, their non-linearity coefficient is relatively small and on the order of 3-7. Referring to SiO resistors for low-voltage applications, the number of grain boundaries should be reduced due to a high C value per one grain boundary. In consequence a problem arises wherein a reduction in the number of grain boundaries would lead to a drop of voltage resistance. Turning to the ZnO base resistors, they are advantageous in that they can be used in a wider range of voltage, since they generally have a coefficient of non-linearity of as high as 10-50 and a reduced grain size. However, ZnO resistors are disadvantageous in that it is difficult to produce the resistors since their non-linearity deteriorates with the lapse of time due to the chemical unstability of their main component ZnO. Thus, an increase in production cost occurs.